I am finishing my basement. Shower is done, toilet is done, just installed vanity, sink, faucet, and drain. But the sink drains really slow when there is a small amount of water in the sink. But if I fill up the sink fairly full, then open the stopper, the water drains very quickly.

Two potential problems I see: (1) sink is vented four feet from drain (I believe code is 3'), (2) tailpiece is 1.25" and trap is 1.5". Anyone have any experience with this?

Hi Marc,

"Two potential problems I see: (1) sink is vented four feet from drain (I believe code is 3'), (2) tailpiece is 1.25" and trap is 1.5". Anyone have any experience with this?"
(1) 2" drain line 5 feet from drain. 1 1/2" drain line 3 1/2 feet from drain.
Not to worry.
(2) This is a normal set up. The 1 1/12 trap has a 1 1/2 X 1 1/4" nylon gasket the takes careb of the difference.

The more water you have in the bowl the more head pressure and weight you have pushing the water down the drain. Less water--less pressure so it doesn't drain as fast. One other thing. On some of the newer lavatorys a vent is needed to prevent air lock when draining. Did you installn a bowl type lavatory without a overflow feature? Regards, Tom

Thanks Tom. Yep - I do have a sink without an overflow. It was pretty spendy, so I'm bummed that this is causing problems. Would you recommend pulling up the lav and returning it, opting for a model with an overflow? Or is there something else I can do to help it drain more quickly.

Great forum.

Hi Marc,

I know that Kohler addressed this problem with a special tailpiece that vents.
These types of lavatories are prone to air lock. What's the make of your lavatory? Regards. Tom